HEEEDITY 



See Fig. 49, left column. The eggs are, so far 

 as we can discover, all of a single type. They 



BEE XOTIFER APHID 



AVORABLE 



OA/0/r/OA/S 



\ ^~7^^ 



\y. \ . 



FIG. 49. Diagram of sex-determination in parthenogenesis. 

 First row, nuclear condition of the parthenogenetic mother; 

 second row, of her eggs when they develop without reduction, 

 after forming a single polar cell; third row, condition of the 

 eggs after complete maturation the fertilized egg in each 

 case produces a male; fourth row, nuclear condition of the 

 fertilized egg, always a female. 



undergo maturation in the manner already de- 

 scribed, the chromosomes being reduced to the 



162 



